This invention relates generally to the treatment of spinal conditions, and more particularly, to the treatment of spinal stenosis using devices for implantation between adjacent spinous processes.
The spine is divided into regions that include the cervical, thoracic, lumbar, and sacrococcygeal regions. The cervical region includes the top seven vertebrae identified as C1-C7. The thoracic region includes the next twelve vertebrae identified as T1-T12. The lumbar region includes five vertebrae L1-L5. The sacrococcygeal region includes nine fused vertebrae that make up the sacrum and the coccyx. The vertebrae of the sacrum are identified as the S1-S5 vertebrae. Four or five rudimentary members form the coccyx.
The clinical syndrome of neurogenic intermittent claudication due to lumbar spinal stenosis is a frequent source of pain in the lower back and extremities, leading to impaired walking, and causing other forms of disability in the elderly. Although the incidence and prevalence of symptomatic lumbar spinal stenosis have not been established, this condition is the most frequent indication of spinal surgery in patients older than 65 years of age.
Lumbar spinal stenosis is a condition of the spine characterized by a narrowing of the lumbar spinal canal. With spinal stenosis, the spinal canal narrows and pinches the spinal cord and nerves, causing pain in the back and legs. It is estimated that approximately 5 in 10,000 people develop lumbar spinal stenosis each year. For patients who seek the aid of a physician for back pain, approximately 12%-15% are diagnosed as having lumbar spinal stenosis.
Common treatments for lumbar spinal stenosis include physical therapy (including changes in posture), medication, and occasionally surgery. Changes in posture and physical therapy may be effective in flexing the spine to decompress and enlarge the space available to the spinal cord and nerves—thus relieving pressure on pinched nerves. Medications such as NSAIDS and other anti-inflammatory medications are often used to alleviate pain, although they are not typically effective at addressing spinal compression, which is the cause of the pain.
Surgical treatments are more aggressive than medication or physical therapy, and in appropriate cases surgery may be the best way to achieve lessening of the symptoms of lumbar spinal stenosis. The principal goal of surgery is to decompress the central spinal canal and the neural foramina, creating more space and eliminating pressure on the spinal nerve roots. The most common surgery for treatment of lumbar spinal stenosis is direct decompression via a laminectomy and partial facetectomy. In this procedure, the patient is given a general anesthesia and an incision is made in the patient to access the spine. The lamina of one or more vertebrae is removed to create more space for the nerves. The intervertebral disc may also be removed, and the adjacent vertebrae may be fused to strengthen the unstable segments. The success rate of decompressive laminectomy has been reported to be in excess of 65%. A significant reduction of the symptoms of lumbar spinal stenosis is also achieved in many of these cases.
Alternatively, the vertebrae can be distracted and an interspinous process device implanted between adjacent spinous processes of the vertebrae to maintain the desired separation between the vertebral segments. Such interspinous process devices typically work for their intended purposes but they could be improved. Current devices for spacing adjacent interspinous processes are typically preformed, and are not customizable for different sizes and dimensions of the anatomy of an interspinous space of an actual patient. Instead, preformed devices of an approximately correct size are inserted into the interspinous space of the patient. Unfortunately, because of individual differences in patient anatomy, it is possible that such preformed devices may not comfortably fit in the interspinous space. Moreover, current devices may be difficult to implant because of the tissue obstructing the interspinous space. The necessity to have a configuration for current devices that ensures that the device remains in the proper location may also make it difficult to implant the device in a minimally invasive or percutaneous manner. Further, current devices are relatively stiff, which may cause subsidence in the spinous processes contacting the device after implantation. Thus a need exists for improvements to surgical spacers, such as those for spacing adjacent interspinous processes.